This makes sure that unit tests that try to fill up the new-space work
on the GC stress buildbots as well.

R=yangguo@chromium.org
TEST=cctest/test-heap --gc-interval=500 --stress-compaction

Review URL: https://codereview.chromium.org/11416200

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13065 ce2b1a6d-e550-0410-aec6-3dcde31c8c00